Rangefinders are used in many contexts to determine distances between two points. Typically, rangefinders are used to measure a distance between an observer and a target point. There are various methods used to estimate or determine this distance based on several different measurement principles. Some rangefinders, such as stadimeters and sextants, use angle measurements between the top and bottom of the target device to estimate a distance range to the target object. Other rangefinders use optical principles to merge two images of a target object from two lenses by using a mechanical or electronic dial. These rangefinders generally measure the degree of rotation of prisms used in the lens to determine the distance to a target object and include coincidence and stereoscopic rangefinders. For more precise range measurements, active rangefinders can be used, which operated my measuring the time it takes a transmitted energy pulse directed at the target to be reflected back and received at the rangefinder. These active types of range finders may use lasers, sonar, or radar as the transmitted energy pulse. Laser rangefinders tend to be the most common of these active rangefinders because of the accuracy and size afforded by these devices.
Laser rangefinders are used often in the military and sports to measure the distance to a desired target. When used on a shooting device, some of these rangefinders use ballistic adjustment features to compensate for changes in elevation between a shooter and a target. One such rangefinder is disclosed in U.S. Pat. No. 5,914,775 (the '775 patent), issued Jun. 22, 1999 to Hargrove et al. The ballistically adjusted rangefinder disclosed by the '775 includes an angle sensitive transducer and a programmed data processor to calculate the distance to a target. However, once a range is determined by the '755 patent, the patent discloses a moveable sight indicator that moves via a linear actuator to provide a sighting mechanism to correspond to the determined range. This extra movement adds additional complexity over traditionally fixed sights, as well as requiring extra time to become positioned that may let a moving target move outside of a previously determined range by the time the sight is correctly positioned.